Ceramic end effector for micro circuit manufacturing

ABSTRACT

An end effector for installation on a robotic arm for transporting a plurality of semiconductor wafers from one location to another features a ceramic end effector body portion that includes a plurality of wafer engaging fingers that each feature wafer support pads. The wafer support pads are adapted to support a semiconductor wafer surface, and at least one of the support pads has a vacuum orifice. The pads are replaceable and/or removable in case of damage or contamination. The support pads are attached to the body in such a way as to allow differential thermal expansion so as to prevent introduction of stress into the components. Typically, a wire spring is employed to secure the pad to the end effector. The body portion features an interior vacuum passageway having a first end that is adapted to connect to a vacuum source and a second end that terminates at the vacuum orifices such that a reduced gas pressure at the first end causes a vacuum to be exerted at the vacuum orifices. The interior passageway is formed from a groove in the end effector body portion and an end effector backplate that is sealingly connected to the end effector body portion to completely cover the groove from the first end to the second end. The ceramic body portion can be made of alumina or silicon carbide.

RELATED APPLICATION

The present application is a continuation-in-part application of U.S.application Ser. No. 10/305,731, filed Nov. 26, 2002 and entitledCERAMIC END EFFECTOR FOR MICRO CIRCUIT MANUFACTURING.

TECHNICAL FIELD

The present invention relates generally to semiconductor waferprocessing and more specifically to an end effector for handlingsemiconductor wafers during processing.

BACKGROUND OF THE INVENTION

Thermal processing systems are widely used in various stages ofsemiconductor fabrication. Basic thermal processing applications includechemical deposition, diffusion, oxidation, annealing, silicidation,nitridation, and solder re-flow processes. Many of these thermalprocesses involve extremely high temperatures. For example, verticalrapid thermal processing (RTP) systems comprise a vertically orientedprocessing chamber that is heated by a heat source such as a resistiveheating element or a bank of high intensity light sources. The heatsource is capable of heating the interior of the processing chamber totemperatures in the range of 450-1400 degrees Centigrade at ramp ratesof up to about 50 degree C./sec.

Semiconductor thermal processing must be performed in an environmentthat is relatively free of contamination. One source of contaminationthat is detrimental to thermal processes is metal. For example, metalssuch as iron, sodium, and chromium in concentrations as little as 1×e¹⁰atoms per cubic centimeter will significantly lower the yield from awafer. Some vacuum type end effectors have metal components such asvacuum lines that make them susceptible to metal contamination withinthe processing chamber.

To maximize throughput and minimize contamination, all of the operationsthat occur during thermal processing of semiconductor wafers areautomated. Robotic handlers routinely move wafers into and out ofprocessing chambers. These handlers often employ end effectors disposedat the end of a robotic arm to grip and manipulate the wafer. Keyfeatures of end effectors include reliable gripping and minimal impacton the wafer surface. One type of end effector features one or morevacuum devices mounted on the end effector that use suction to grip thewafer and to give a positive indication that the wafer is positionedproperly. Some existing vacuum type end effectors have plasticcomponents such as wafer support pads that are not suitable for hightemperature thermal processes because they would melt on contact withthe heated wafer.

SUMMARY OF THE INVENTION

A ceramic end effector with an interior passage for vacuum providesrelatively low cost, lightweight, and contaminate free wafer handlingfor high temperature thermal processing applications.

An end effector for installation on a robotic arm for transporting aplurality of semiconductor wafers from one location to another isprovided that features a ceramic end effector body portion that includesa plurality of wafer support pads. The wafer support pads are adapted tosupport a semiconductor wafer surface, and at least one of the supportpads has a vacuum orifice.

The support pads are secured to the end effector utilizing a uniquespring which through its action forces the support pad in a downwarddirection against the body portion. The spring additionally forces thatpad forward against an angled surface on the body. The pad is thusforced downward and into contact with the body at the angled interfaceas well. The surface of the bottom of the pad and that of the matingsurface of the body are ground to a high degree of flatness to effect aseal that has very low leakage. The pad and body in this configurationmay expand or contract at different rates as well as move relative toeach other without affecting the seal or introducing stressed intoeither component. The underside of the vacuum pad features a counterborewhich when exposed to negative pressure results in a net downward forceagainst the end effector body thus improving the effectiveness of theseal between the pad and the end effector body. The pads areconveniently removable and/or replaceable in the event of damage orcontamination.

The body portion features an interior vacuum passageway having a firstend that is adapted to connect to a vacuum source and a second end thatterminates at the vacuum aperture such that a reduced gas pressure atthe first end causes a vacuum to be exerted at the vacuum aperture. Inone embodiment, the interior passageway is formed from a groove in theend effector body portion and an end effector backplate that issealingly connected to the end effector body portion to completely coverthe groove from the first end to the second end. The ceramic bodyportion can be made of alumina or silicon carbide. In an exemplaryembodiment, the end effector has three wafer engaging fingers, two ofwhich have wafer support pads that include vacuum orifices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overview drawing of a robot featuring an end effectorconstructed according to an embodiment of the present invention loadingan RTP process chamber;

FIG. 2 is a perspective view of the body portion of an end effectorconstructed in accordance with an embodiment of the present invention;

FIG. 2A is a bottom view of an end effector showing the vacuum channelsconstructed in accordance with an embodiment of the present invention;

FIG. 3 is a close-up top view of a vacuum support pad cavity of the endeffector body of FIG. 2 constructed in accordance with an embodiment ofthe present invention;

FIG. 4 is a cross-sectional view of the vacuum support pad cavity ofFIG. 3;

FIG. 5 is a top view of a non-vacuum support pad cavity of the endeffector body of FIG. 2 constructed in accordance with an embodiment ofthe present invention;

FIG. 6 is a cross-sectional view of the non-vacuum support pad cavity ofFIG. 5;

FIG. 7 is a close-up top view of a vacuum support pad mounted in itsoperating position constructed in accordance with an embodiment of thepresent invention;

FIG. 8 is a cross-sectional view of the vacuum support pad cavity ofFIG. 7;

FIG. 9 is a close-up top view of a non-vacuum support pad mounted in itsoperating position constructed in accordance with an embodiment of thepresent invention; and

FIG. 10 is a cross-sectional view of the non-vacuum support pad cavityof FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows an overview of an end effector 20 installed on a typicalwafer handling robot 15 that is loading an RTP machine 30. The endeffector 20 grips a wafer 17 and installs it through a slot 36 into theRTP processing chamber. Upon completion of the thermal process, the endeffector is inserted into the processing chamber and retrieves the wafer17 for transport to the next step in fabrication.

FIGS. 2-6 show the end effector 20 according to the present invention inmore detail. The end effector 20 includes a body portion 25 that is madeof a ceramic material such as, alumina, or silicon carbide, butpreferably alumina. The body portion 25 is generally planar in shape andfeatures a robot arm mounting end 19, and two outer wafer engagingfingers 27 and a center wafer support finger 29 at an axial end. Theouter wafer engaging fingers 27 and support 29 each have a wafer supportpad cavity which houses a wafer support pad that support the waferduring handling without damaging the wafer surface. The wafer supportingend of each wafer engaging finger 27 includes a flared wall portion 27 ain the same plane as the finger 27. This flared wall region 27 aencompasses the vacuum support pad cavity 31. The center wafersupporting finger 29 includes a non-vacuum support pad cavity 81.

Within the body portion 25, an interior vacuum passageway 37 (shown inphantom in FIG. 2) passes from the robot mounting end 19 to vacuumapertures 34 located on each wafer engaging finger 27. The vacuumpassageway 37 is formed from a groove that is machined in the surface ofthe body portion 25 that is opposite the surface that includes the wafervacuum support pads 33 (FIGS. 7 and 8). A backplate 35 (FIG. 2 b) isfused to the body portion over the groove 37 to seal the passageway sothat vacuum can pass from the robot mounting end 19 to the vacuumapertures 34. Known vacuum fittings are located in the robot mountingend 19 to connect the interior vacuum passageway to an exterior vacuumsupply 21. Of course, exterior vacuum lines (not shown) could be used inconjunction with or in lieu of the interior vacuum passageways describedherein in accordance with the present invention. The center support 29does not include vacuum grooves. The center support 29 does include anon-vacuum support pad cavity 81 which houses a non-vacuum support pad77

FIGS. 3 and 4 show the details of the vacuum support pad cavity 31. Thevacuum support pad cavity 31 is a substantially circular cavity, thebottom of which is a flat vacuum sealing surface 57. The vacuum supportpad cavity 31 further includes a front beveled wall portion 54 whichangles into the body of the support finger 27 and away from a centralaxis of the vacuum support pad cavity 31. This makes the opening cavitydiameter smaller than the diameter of the cavity along the vacuumsealing bottom portion 57. As described, a vacuum passageway 37 runs thelength of the supporting finger 27 and terminates at a vacuum aperture34 in the sealing surface 57 of the vacuum support pad cavity 31. Inthis configuration, vacuum is supplied to the vacuum support pad cavity31 through the vacuum aperture 34.

Referring now to FIGS. 7 and 8, a vacuum support pad 33 is secured inthe vacuum support pad cavity 31 by a removable nickel-chromium alloywire spring 50, typically Inconel wire. The arrangement of the vacuumsupport pad 33 and wire 50 permit differential thermal expansion betweenthe vacuum support pad 33 and the end effector body 27 while maintainingthe integrity of the seal between the vacuum support pad 33 and the base57. The vacuum support pads 33, in turn, are consumable and/orreplaceable in the event that they become damaged or contaminated.

The wire spring 50 extends through a first section of the flared wallportion 27 a in a bore 53 a. The bore 53 a terminates at the outerperipheral edge of the vacuum support pad cavity 31 thus exposing thewire spring 50 to the vacuum support pad cavity 31. The wire spring 50further extends across the entire length of the vacuum support padcavity 31 into a bore 53 b in a second section of the flared wallportion 27 a. The bore 53 b extends through the second section of theflared wall portion 27 b providing a path for the wire spring 50 toextend through and protrude out of the flared wall portion 27 b. Thearea of the wire spring 50 that is exposed in the vacuum support padcavity 31 provides torsional forces on a vacuum support pad 33 withinthe vacuum support pad cavity 31. The torsional forces from the spring50 are a result of the vacuum support pad 33 in the vacuum support padcavity 31 displacing the wire spring 50 from its natural position withinthe vacuum support pad cavity 31. In this arrangement, the wire spring50 forces the vacuum support pad 33 forward and downward to make contactthe beveled wall 54 of the vacuum support pad cavity 31.

FIG. 8 shows the vacuum support pad 33 in its proper operating position.The vacuum support pad 33 includes top surface 61 having a raisedannular wafer engaging surface 63. A vacuum enhancing chamber is createdbetween the top surface 61 and the raised annular surface 63 which aidsin securing a wafer against the annular surface 63 during operation andmovement of the robotic arm. At the central axis of the vacuum supportpad 33 is a vacuum orifice 65 which extends completely through the bodyof the vacuum support pad 33. The outside perimeter of the vacuumsupport pad 33 includes a beveled wall 67 which angles away from thecentral axis A of the vacuum support pad 33 from the top of the annularsurface 63 to the bottom of the vacuum support pad 33. When the vacuumsupport pad 33 is positioned in the vacuum support pad cavity 31 asdescribed above, the wire spring 50 applies a torsional force that urgesthe vacuum support pad 33 towards the beveled wall portion 54 of theinterior of the vacuum support pad cavity 31. The beveled wall 67 of thevacuum support pad 33 is caused to come into contact with the beveledwall 54 of the interior of the vacuum support pad cavity 31 in mannerthat locks a portion of the vacuum support pad 33 within the vacuumsupport pad cavity 31. The wire spring 50 rests on the outer perimeterof the pad including the bevel which causes the wire spring 50 tofurther exert a downward force on the vacuum support pad 33.

The pad further includes a bottom surface 71 having a portion of whichis raised creating an annular sealing surface 73. The sealing surface 73sealingly engages the bottom surface 57 of the vacuum support pad cavity31. Both the annular sealing surface 73 of the vacuum support pad 33 andthe bottom surface 57 of the vacuum support pad cavity 31 are ground toa relatively high degree of flatness to provide a seal with very lowleakage. The bottom surface 71 further includes a counter bore area 75having the vacuum orifice 65 generally it's center. During operation,the vacuum aperture 34 is in fluid communication with the vacuum orifice65 of the vacuum support pad 33 such that a vacuum pressure can becommunicated through the vacuum support pad 33 to a wafer contacting thewafer engaging surface 63. Further, the counter bore area 75 whenexposed to the negative pressure of the vacuum enhances the net downwardforce of the vacuum support pad 33 resulting in the annular sealingsurface 73 of the vacuum support pad 33 to sealingly engage with verylow leakage the bottom 57 surface of the vacuum support pad cavity 31.

FIGS. 5 and 6 illustrate the pad holding end of the central supportfinger 29. As with the holding end of the wafer engaging fingers 27, thesupport finger 29 includes a non-vacuum support pad cavity 81 which isused to house a non-vacuum support pad 77. The non-vacuum support cavity81 further includes the front bevel wall 54 and a flat bottom 61.However, the wafer support finger 29 does not include vacuum passagewaysand for this reason, the flat bottom 61 of the vacuum support pad cavity31 does not include a vacuum aperture.

Turning now to FIGS. 9 and 10, a support finger 29 is illustrated. Thesupport finger 29 includes a non-vacuum support pad cavity 81 at aportion of the support finger 29 distal to the robot mounting end 19.The non-vacuum support pad cavity 81 is generally circular in shape. Thenon-vacuum support pad 77 is held in place within the non-vacuum supportpad cavity 81 in the same manner as described for the wafer engagingfinger 27. The cavity wall 29 a includes bores 83 a and 83 b, extendingthrough the entire wall 29 a. A spring clip 50 extends through a firstsection of the cavity wall 29 a, across the entire length of thenon-vacuum support pad cavity 81 and further through the second sectionof the cavity wall 29 b, as shown. The spring clip 50 is exposed to thenon-vacuum support pad cavity 84 and, as described with respect to thewafer-engaging finger 27, arranged to make torsional contact with thenon-vacuum support pad 77.

The non-vacuum support pad cavity 81 extends partially into the body ofthe support finger 29 and includes a wall bevel 85 that angles into thebody and away from the central axis of the non-vacuum support pad cavity81. The non-vacuum support pad 77 includes a wafer engaging surface 87and a support engaging surface 89. The support engaging surface 89 has agreater diameter than the wafer engaging surface 87 creating the wallbevel 85 around the outer perimeter of the non-vacuum support pad 77.When the non-vacuum support pad 77 is in its operational location, thewire spring 50 rests on the bevel 85 providing torsional force to thenon-vacuum support pad 77. This force, because of the bevel, causes thenon-vacuum support pad 77 to be forced downward against the non-vacuumsupport pad cavity bottom 91 and forward into the beveled wall 85. Thebevel on the outer perimeter of the non-vacuum support pad 77 interlockswith the wall bevel 85 in the non-vacuum support pad cavity wall, thuslocking the non-vacuum support pad 77 in the non-vacuum support padcavity 81. The support finger 29 does not include a vacuum passagewayand, as such, the non-vacuum support pad 77 does not require a vacuumorifice nor does the cavity bottom 91 include a vacuum aperture. Thenon-vacuum support pad 77 merely supports a portion of a wafer duringoperation of the robotic arm 20.

Although the present invention has been described with a degree ofparticularity, it is the intent that the invention include allmodifications and alterations from the disclosed design falling withinthe spirit or scope of the appended claims.

1. For use in the processing of semiconductor wafers, an end effectorfor installation on a robotic arm for transporting a plurality ofsemiconductor wafers from one location to another, the end effectorcomprising: a ceramic end effector; a plurality of removable wafersupport pads disposed at a distal end of said end effector said supportpads being adapted to support a semiconductor wafer surface, wherein atleast one of the support pads comprises a vacuum orifice incommunication with a vacuum source for exerting a vacuum on the wafersurface; and a retaining structure for removably securing the removablesupport pads to the end effector.
 2. The end effector of claim 1 whereinsaid end effector body includes an interior vacuum passageway having afirst end that is adapted to connect to a vacuum source and a second endthat terminates at a vacuum aperture, said aperture communicating withthe support pad vacuum orifice such that a reduced gas pressure at thefirst end causes a vacuum to be exerted at the vacuum orifice of thesupport pad.
 3. The end effector of claim 2 wherein the interiorpassageway is formed from a groove in the end effector body portion andan end effector backplate that is sealingly connected to the endeffector body portion to completely cover the groove from the first endto the second end.
 4. The end effector of claim 1 wherein the ceramicbody is made of alumina.
 5. The end effector of claim 1 wherein theceramic body is made of silicon carbide.
 6. The end effector of claim 1wherein the end effector body comprises a plurality of wafer engagingfingers at the distal end.
 7. The end effector of claim 6 wherein thewafer support pads are disposed at an axial end of the wafer engagingfingers.
 8. The end effector of claim 6 comprising three wafer engagingfingers, two of which comprise wafer support pads that include vacuumorifices.
 9. The end effector of claim 6 wherein at least one of thewafer engaging fingers includes a cavity which houses a vacuum supportpad.
 10. The end effector of claim 1 wherein said retaining structure isa spring clip, said spring clip extending through a portion of the bodyof the wafer engaging finger, into said cavity and making torsionalengagement with the vacuum pad such that said spring clip secures thepad in the cavity.
 11. The end effector of claim 1 wherein the vacuumsupport orifice includes a counterbore to enhance a seal between thevacuum pad and end effector during expansion or contraction of the endeffector components.
 12. The end effector of claim 1 wherein the vacuumpad is ground flat at that portion which engages the end effector tocreate a vacuum seal with low leakage.
 13. For use in the processing ofsemiconductor wafers, an end effector for installation on a robotic armfor transporting at least one of semiconductor wafers from one locationto another, the end effector comprising: a ceramic end effector bodyportion including a plurality of wafer engaging fingers; a plurality ofremovable wafer support pads disposed at an axial end of the waferengaging fingers, said support pads being adapted to support asemiconductor wafer surface, wherein at least one of the support padscomprises a vacuum orifice in communication with a vacuum source forexerting a vacuum on the wafer surface; and a retaining structure forremovably securing the removable support pads to the end effector. 14.The end effector of claim 13 wherein the ceramic body is made ofalumina.
 15. The end effector of claim 13 wherein the ceramic body ismade of silicon carbide.
 16. The end effector of claim 13 wherein atleast one of the wafer engaging fingers includes a cavity which houses avacuum support pad.
 17. The end effector of claim 13 wherein saidretaining structure is a spring clip, said spring clip extending througha portion of the body of the wafer engaging finger, into said cavity andmaking torsional engagement with the vacuum pad such that said springclip secures the pad in the cavity.
 18. The end effector of claim 13wherein the vacuum support orifice includes a counterbore to enhance aseal between the vacuum pad and end effector during expansion orcontraction of the end effector components.
 19. The end effector ofclaim 13 comprising three wafer engaging fingers, two of which comprisewafer support pads that include vacuum orifices.
 20. The end effector ofclaim 13 wherein at least one of the wafer engaging fingers includes acavity which houses the vacuum support pad.
 21. For use in theprocessing of semiconductor wafers, an end effector for installation ona robotic arm for transporting at least one of semiconductor wafers fromone location to another, the end effector comprising: a ceramic endeffector body including three wafer engaging fingers, at least one ofwhich comprise wafer support pads that include vacuum orifices; aplurality of removable wafer support pads disposed in a cavity at anaxial end of the wafer engaging fingers, said support pads being adaptedto support a semiconductor wafer surface, wherein at least one of thesupport pads comprises a vacuum orifice in communication with a vacuumsource for exerting a vacuum on the wafer surface; and a retainingstructure comprising a spring clip, said spring clip extending through aportion of the body of the wafer engaging finger, into said cavity andmaking torsional engagement with the pad such that said spring clipsecures the pad in the cavity.
 22. For use in the processing ofsemiconductor wafers, an end effector for installation on a robotic armfor transporting at least one of semiconductor wafers from one locationto another, the end effector comprising: a ceramic end effector bodyincluding an interior vacuum passageway having a first end that isadapted to connect to a vacuum source and a second end that terminatesat a first vacuum orifice such that a reduced gas pressure at the firstend causes a vacuum to be exerted at the fist vacuum orifice; aplurality of removable wafer support pads secured to said end effectorbody portion said support pads being adapted to support a semiconductorwafer surface, wherein at least one of the support pads comprises asecond vacuum orifice in communication with said first vacuum orificesuch that a vacuum is exerted on the wafer surface; and a retainingstructure for securing the removable support pads to the end effector.23. A method of securing a semiconductor wafer support pad to an endeffector, said end effector for use in thermal processing of thesemiconductor wafer wherein the end effector is installed on a roboticarm for transporting at least one of semiconductor wafers from onelocation to another, the method comprising the steps of: placing aplurality of wafer support pads in contact with the end effector,wherein at least one of said pads including a vacuum orifice incommunication with a vacuum source; and securing the wafer support padsto the end effector with a retaining structure.
 24. The method of claim23 wherein the end effector comprises a plurality of wafer engagingfingers.
 25. The end effector of claim 24 wherein the wafer support padsare disposed at an axial end of the wafer engaging fingers.
 26. Themethod of claim 25 wherein at least one of the wafer engaging fingersincludes a cavity which houses the vacuum support pad.
 27. The method ofclaim 26 wherein said retaining structure is a spring clip, said springclip extending through a portion of the body of the wafer engagingfinger, into said cavity and making torsional engagement with the padsuch that said spring clip secures the pad in the cavity